A can finish a work in 15 days. B can finish the same work in 25 days. They work together for 5 days, after which B was replaced by C and the rest of the work in finished by A and C in next 4 days. Then C alone can finish the work in:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 20 days.
Given that
A can finish a work in 15 days
B can finish the same work in 25 days
A and B work together for 5 days,
The remaining work is completed by A and C in 4 days
According to the question
Total work = LCM (15, 25) = 75
The efficiency of A = 75/15 = 5
The efficiency of B = 75/25 = 3
The work is done by A and B = (5 + 3) × 5 = 40
The remaining work (75 - 40 = 35) is done by A and C = 35/4 = 8.75
Now, the efficiency of C = 8.75 - 5 = 3.75
Hence, C alone can finish the work in = 75/3.75 = 20 days